Presently titanium oxides are widely used in industry for various applications: Paint pigment, opacifying agent, welding rod fluxes, optical coatings, as a catalyst (for example in NOx absorption from flow gases), ceramic finish coat, plastics elastomers, printing inks, roofing granules, glass, and in glazes. The forecasted growth through 2006 is 2.0% per year.
Titanium oxides have at least four crystal forms: titanic acid, anatase, brookite, and rutile. Of these, the rutile form has the greatest density, hardness, and refractive index Titanium oxide crystals are characterized by the variety of sizes, colors, densities, porosities, surface areas and shapes. These parameters have great impact on their use and performance. The final product properties depend on the procedures developed for precipitation and aging of the products. There is great interest in a technique for the production of titanium oxide particles with advanced properties, such as nano-crystallinity, narrow particle size distribution, preparation of metastable phases etc.
As presented in U.S. Pat. Nos. 6,830,742 and 6,653,356 titanium oxide is generally produced using a liquid phase process, where titanium tetrachloride or titanyl sulfate is used as a starting material which is hydrolyzed in a hydrophilic solvent or a vapor phase process, in which a volatile starting material such as titanium tetrachloride is vaporized, and then reacted in the gas state with an oxidizing gas such as oxygen or steam, at a high temperature.
In general, the titanium oxide powder produced by the liquid or vapor phase process disadvantageously undergoes heavy aggregation and wide range of particle size distribution. In the case of titanium oxide produced by the vapor phase process, the same problems that are occurring through production via the liquid phase process, are occurring as well in this process. That is, although ultra fine particulates of titanium oxide may be obtained through the conventional vapor phase process, only particulates of titanium oxide that have undergone grain growth can be obtained. Therefore, there is great interest in a technique for the production of titanium oxide materials with advanced properties, such as nano-crystallinity, narrow particle size distribution, preparation of meta-stable phases etc.
The main objective of the present invention is to provide an industrial and economical process for the production of titanium oxide particles characterized by a desired particle size, size distribution and crystal habit.
Another objective of the present invention is to provide an industrial and economical process for the production of titanium oxide particles characterized by a low hydration level.
Another object of the present invention is to provide an industrial and economical process for the production of titanium oxide particles characterized by high porosity and by the required morphology and habit.